A big advantage of the Michigan setup is that drivers who are unable to find a gap in traffic during the permissive left-turn phase can complete their turn during the protected lagging left-turn phase. This prevents drivers from getting “stuck” in the middle of the intersection.

The FYA setup allows for much greater flexibility which can often lead to complicated left-turn phasing. The video below shows a lead-lag FYA intersection where one direction has a protected leading left-turn while the opposing direction has a protected lagging left-turn:

Watching 1:30-1:35 in the video, the left-turn is flashing yellow as the thru is clearing down. Even though this is not a yellow trap, it could be argued that it is a “perceived yellow trap”. A driver sees in their peripheral vision that the thru lane is changing to yellow and quickly glances up to see a solid yellow left-turn arrow. Unfortunately, the driver glanced up during the 0.5 second flash on as opposed to the 0.5 second flash off and they mistakenly believed the left turn was terminating. This “perceived yellow trap” would be just as dangerous as an actual yellow trap. A traffic engineer could easily argue the theory of why the operation from 1:30-1:35 is safe, but in reality is it?

Virginia = Doghouse with few exceptions (one or two intersections in VA Beach, redundant side-mounted signals in Arlington), though 5-section towers used to be used with some regularity for protected/permissive right turn signals. Very few of these remain. Even most VDOT-installed side-mounted protected/permissive signals are doghouses astro-braced to the pole or pedestal despite how odd they look. In the extreme southwest portion of the state (Bristol, etc.), the WV variation of the doghouse is used.

Pennsylvania = Doghouse with few exceptions, even when side-mounted. Even many of their 4-section signals are of this style (i.e. the green arrow and green ball are next to each other below the yellow and red ball).

Ohio = Same as Pennsylvania

South Dakota = 5-Section towers. I've never seen a doghouse.

California = Both -- Overhead are usually doghouse, side-mounted are always 5-section towers.

Washington, DC = Same as California

Maryland = Doghouse for most overhead signals, though some supplemental signals on the close side of the intersection sometimes use an odd combination of 12-inch signals for the arrows and 8-inch signals for the red, yellow, and green balls, in a WV-modified doghouse formation. (http://farm5.staticflickr.com/4047/4416770363_244aea0434_o.jpg). I've seen 5-section towers used for side-mounted signals, when used.

The most obvious VA exception I forgot about. Did Charlottesville use doghouses for their installs before the signals with bimodal arrows were installed? The earliest I recall considering the signals of Charlottesville was around 1999, marveling at the rare use (for VA) of the bimodal arrows. I could've sworn I saw a doghouse somewhere (not the 3M) but it may have been in Albemarle County.

Come to think of it Illinois uses bimodal arrows (4 light towers) in some places as well, particularly around Champagne/Urbana if my memory serves me well.

The first time I saw one was in Bethesda, MD in the mid-1990s... is that about when bimodal arrows started being installed?

The thing I found most interesting about the Charlottesville videos linked above was the weird right-on-red sign on 10th Street at Grady Avenue. Street View with a curb-mounted sign may be seen here. I can't say I've ever seen a sign like that before, including at that intersection (the sign was definitely not there when I attended UVA because I'd remember something like that). The message is straightforward enough, though I wonder if it might be a bit wordy when you see it in person. If I remember, I will have to drive past it when we go to a football game this fall.

(That whole intersection complex was always weird. Going west on Preston Avenue, the light would turn red for traffic turning left onto Grady but stay green to continue straight on Preston. Immediately afterwards the intersection of Preston and 10th had a flashing yellow light that's now gone. So anyone who knew the area would go straight on Preston, hang a left at the flashing yellow, and then go right on red onto Grady. Saved you a long wait at the left-turn light.)

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you—I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

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"You know, you never have a guaranteed spot until you have a spot guaranteed."—Olaf Kolzig, as quoted in the Washington Times on March 28, 2003,commenting on the Capitals clinching a playoff spot.

"That sounded stupid, didn't it?"—Kolzig, to the same reporter a few seconds later.

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you—I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

Are the left turns permissive? A lead-lag can be dangerous as it has the potential (depending how the signal is set up) to lead to the yellow trap. The video i posted previously is an example of a FYA lead-lag setup. The protected turn is allowed to skip if nobody is detected which leads to some interesting phasing. The FYA effectively eliminates the possibility of the yellow trap but it can still lead to what i call the "perceived yellow trap". Does anyone think the signal phasing from 1:30 through 1:35 in the video could be confusing to some drivers and lead to a perceived yellow trap?

what is the yellow trap? assuming that, because your straight-through travel lanes are getting red, so are the opposing straight-through travel lanes? and therefore that oncoming traffic is gonna stop?

dangerous assumption. first off, you cannot assume anything about the opposing signal. second, if you think oncoming traffic is gonna stop when they get a yellow, instead of flooring it, you have not driven in any major city on the coasts.

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you—I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

Are the left turns permissive? A lead-lag can be dangerous as it has the potential (depending how the signal is set up) to lead to the yellow trap. The video i posted previously is an example of a FYA lead-lag setup. The protected turn is allowed to skip if nobody is detected which leads to some interesting phasing. The FYA effectively eliminates the possibility of the yellow trap but it can still lead to what i call the "perceived yellow trap". Does anyone think the signal phasing from 1:30 through 1:35 in the video could be confusing to some drivers and lead to a perceived yellow trap?

The one I mentioned before is definitely permissive, using the four-section signal mentioned previously. Here's a Street View of the intersection I referenced: http://goo.gl/maps/L1TXO

I am not positive they still use lead-lag at that particular intersection because nowadays I'm usually there on football game days and the cops override the signal to flash yellow. Either way, though, that particular cycle (coupled with permissive left turns) was peculiar to Charlottesville among Virginia jurisdictions I've visited regularly.

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"You know, you never have a guaranteed spot until you have a spot guaranteed."—Olaf Kolzig, as quoted in the Washington Times on March 28, 2003,commenting on the Capitals clinching a playoff spot.

"That sounded stupid, didn't it?"—Kolzig, to the same reporter a few seconds later.

The most obvious VA exception I forgot about. Did Charlottesville use doghouses for their installs before the signals with bimodal arrows were installed? The earliest I recall considering the signals of Charlottesville was around 1999, marveling at the rare use (for VA) of the bimodal arrows. I could've sworn I saw a doghouse somewhere (not the 3M) but it may have been in Albemarle County.

Only within city limits are there bimodal arrows. Inside Charlottesville, there are no 5-section signals (besides the 3M). Only 4-sections with bimodal arrows.Outside Charlottesville, there are no 4-section w/ bimodal arrows. Only doghouses. The closest doghouse signals in Charlottesville are at JPJ, outside of city limits.

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The first time I saw one was in Bethesda, MD in the mid-1990s... is that about when bimodal arrows started being installed?

I honestly know little about bimodal arrow 'history'. Before LEDs were used for signals, there were fiber-optic bimodal arrows. Right now, all bimodal arrows in Charlottesville are LED except for 1 fiber-optic arrow (and it is currently not functioning).

In Charlottesville, there are two versions of LED bimodal arrows.

This arrow has clear glass, so you can see how it works. This video shows it changing close up and from a distance, then shows them in slow motion. You can see how there are alternatingly-colored LED lights in rows to form the arrow, so it noticably shifts a little when changing color.

Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball.

That intersection no longer does that. There are two ways it cycles.

[1] If there is someone waiting to turn left NB on Emmet, but noone waiting SB on Emmet (it cycles vice versa too):

Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball.

That intersection no longer does that. There are two ways it cycles.

....

That's a big improvement. I recall seeing any number of near-misses over the years when people, mostly non-locals who weren't aware that Charlottesville used this peculiar phasing, would be hit by a yellow trap, essentially—they'd be waiting on the permissive green during the "both directions green ball" phase, see their side go red, and proceed to turn under the erroneous assumption the other side was also going red. (This is one of the problems with the habit of pulling out into the intersection to wait during a permissive green cycle.)

Logged

"You know, you never have a guaranteed spot until you have a spot guaranteed."—Olaf Kolzig, as quoted in the Washington Times on March 28, 2003,commenting on the Capitals clinching a playoff spot.

"That sounded stupid, didn't it?"—Kolzig, to the same reporter a few seconds later.

what is the yellow trap? assuming that, because your straight-through travel lanes are getting red, so are the opposing straight-through travel lanes? and therefore that oncoming traffic is gonna stop?

What is the yellow trap? A "yellow trap" occurs when a driver, who has a permissive left turn phase and is waiting for a gap in the opposing through movement, sees a yellow indication for both through and left turns, and mistakenly thinks that the signals for the opposing direction have become yellow simultaneously.

The operation at 1:30-1:35 in the video is NOT a yellow trap, but drivers may be confused when they see the thru lanes turning yellow. The driver may automatically assume that the thru must terminate simultaneous with the opposing thru… or they may glance up for a split second – less than the 0.5 second flash rate - to see that the left turn signal is solid yellow, not realizing that it is still in fact blinking. The intersection in the video is at 9 Mile & Harper in Macomb County, Michigan. The woman who is speaking in the video was involved in a crash on 2/15/11 while attempting to make a left turn traveling NB Harper. You can hear her adamantly saying that she made a left turn while all three signal heads were turning yellow together (listen to her at the very end of the video). In the UD-10 report, the officer stated that the opposing thru driver entered the intersection while the light was green. Maybe in her mind, the left turn had a solid yellow when in fact it was still flashing yellow. It's similar to driving through a signal in flash and for a moment believing you're about to run the yellow light (for example, when you are driving behind a large truck and can't see the flashing signal until the last moment).

The phasing is complicated by the fact that the very next cycle, the thru and left turn does terminate together. This is due to the fact that nobody was detected in the opposing left turn lane and that phase was allowed to skip. It's confusing to drivers when the signal phasing is changing on a cycle by cycle basis as drivers never really know what to expect.